Berlin 2024 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 35: Superconducting Electronics: SQUIDs, Circuit QED

TT 35.8: Talk

Wednesday, March 20, 2024, 11:30–11:45, H 2053

Phase locking squeezed states of microwave light — Lukas Danner^{1, 2}, Florian Höhe², Ciprian Padurariu², Joachim Ankerhold², and •Björn Kubala^{1, 2} — ¹Institute of Quantum Technologies, German Aerospace Center (DLR), Ulm, Germany — ²ICQ and IQST, Ulm University, Ulm, Germany

Squeezed states of light constitute an important resource for various quantum technological applications, such as using the reduced fluctuations for metrology or the entanglement of a two-mode squeezed state for teleportation or quantum illumination. For all these applications stabilization of the phase is crucial. Josephson photonics devices, where microwave radiation is created by inelastic Cooper pair tunneling across a dc-biased Josephson junction in-series with a microwave resonator, are particularly vulnerable as they lack the reference phase provided by an ac-drive. This hampers, for instance, the direct measurement of entanglement [1]. We recently developed a full quantum mechanical theory [2] describing, first, how the intrinsic shot noise of the Josephson-photonics device inevitably diffuses the oscillators phase and how, second, the phase and frequency of the emission can be locked to a weak ac-input. Based on this theory, we show here, how locking mechanism and features change, if Josephson-photonics devices are operated at a resonance, where pairs of photons and thus squeezed radiation are created.

[1] A.Peugeot et al., Phys. Rev. X 11 (2021) 031008

[2] F. Höhe et al., arXiv:2306.15292.

Keywords: Josephson junction; Synchronization; Locking; Squeezing